Medical efforts to treat pain, known as “pain management”, address a large market, as clinical pain is a worldwide problem with serious health and economic consequences. For example, in the United States, medical economists estimate that the effects of pain result in approximately $100 billion (USD) in costs annually, including an estimated $515 million (USD) in lost work days. According to the National Institute of Health, approximately 40 million Americans are unable to find relief from their pain. This includes approximately one million cancer patients that suffer from severe pain at any given time, and an estimated 10% of the more than 200,000 AIDS patients that suffer severe pain.
Drugs are a key element in the treatment of pain. The worldwide market for pain was about $40.7 billion in 2004. The pain management market has grown immensely in recent years and is expected to continue to grow significantly. The pain management market has grown by more than 34% per year during the past five years. This is likely due to a number of factors, such as, a rapidly aging population, patient demand for rapid effective pain relief, increasing recognition of the therapeutic and economic benefits of rapid and effective pain management by physicians, healthcare providers and payers, and longer survival times for patients with painful chronic conditions, such as cancer and AIDS.
Many different kinds of pain exist including acute, chronic, persistent and breakthrough pain. As well, there exist different approaches to treat pain. Opioids are typically prescribed to manage moderate-to-severe acute or chronic breakthrough pain due to the fact that fast-acting, short-lived opioids can provide rapid delivery. The most common acute use of opioids is for post-surgical pain. Opioid drugs used to treat acute pain include intravenous fentanyl, hydrocodone and oral oxycodone, which provide rapid pain relief. Intravenous therapy, however, is expensive and is suitable for hospitalized patients only.
The route of administration of any medication is an important consideration. Although many patients prefer oral administration of medications, oral medication is not always “fast-acting”, a property which is clearly desirable in the treatment of acute breakthrough pain, for example. Also, orally administrable medications are generally provided in the form of solid shaped articles such as tablets, pills, caplets and capsules that retain their shape under moderate pressure. Some patients, particularly pediatric and geriatric patients, have difficulty administering an oral medication due to inability to swallow, nausea or other gastrointestinal problems. Breakthrough pain medications can be taken in other ways, including by injection, under the tongue (sublingual), rectally, or transmucosally absorbed in the mouth but not swallowed; however, these forms of administration are often not as “fast-acting” as would be desired.
Liquid, syrups or suspensions are an alternative to solid dosage forms and are often preferred for pediatric and geriatric patients who have problems swallowing tablets. However, these dosage forms can be difficult to measure accurately and administer easily. Liquid formulations often deteriorate rapidly upon exposure to heat or other atmospheric conditions and consequently have a relatively short shelf life. Furthermore, liquid formulations require a relatively large volume and are bulky to store.
The bitter after-taste of many drugs which are orally administered, such as tablets, capsules or suspensions, often contributes to patient non-compliance in taking medicine. Apart from the taste of a chewable nutritional supplement, the ‘mouth-feel’ of the supplement must also be taken into account. ‘Mouth-feel’ is a concept that encompasses non-taste-related aspects of the sensation experienced by a person while chewing or swallowing a nutritional supplement. Aspects of mouth-feel include, for example, the hardness and brittleness of a composition, whether the composition is chewy, gritty, oily, creamy, watery, sticky, easily dissolved, astringent, effervescent, and the like, and the size, shape, and form (tablet, powder, gel, etc.) of the composition.
In view of the foregoing, there remains a need to develop a formulation for the oral delivery of a pharmaceutical agent that overcomes at least one of the disadvantages of prior formulations.